We were hiking through the Wonderopolis jungle the other day on our way to the beach when we stopped to take a break under a big shade tree. We were about to close our eyes for a short siesta when we overheard a monkey and a sloth having an interesting conversation in the branches above us:

Monkey: Hey Sloth! Wake up! Did you know you can see all the way to the beach from up here?

Sloth: I'm awake, Monkey. Wow! Look at all the humans on the beach. What are they doing?

Monkey: They call it sunbathing. I don't get it. They just lie there on the sand and sweat.

Sloth: Why would they do that when they could nap in a nice, cool tree?

Monkey: They would need a lot of trees. Look at all of them! How many are there? Help me count. 1...2…3…4…no, wait, did I already count that one?

We couldn't nap with those two chattering above us, so we moved on down the path. Their conversation did make us WONDER about population, though. We already have an idea of how many humans there are on Earth, but we were curious about how many animals of all kinds there are in the world.

Unfortunately, that question doesn't have an easy answer. Scientists who have tried to answer it have only been able to come up with rough estimates that have a wide margin of error.

If you want to understand how difficult it is to get an accurate count of all the animals in the world, we have a challenge for you: count all the animals on the property you call home. This would include your house and the land that it sits on.

Start with the humans in your home. They're easy to count. If you have pets, those are easy to count, too. But there are so many more animals around you. Don't forget the birds and squirrels living outside your home. You also need to count the rabbits, raccoons, mice, and other creatures not easily seen during the day.

If you have a pond on your property, don't forget to count the fish! Finally, you must be sure to count the most populous group of animals in any area: insects. That means you need to count every ant, fly, and mosquito.

If you give this challenge a serious try, you will soon understand the problem that scientists who have considered this question face. There are simply so many animals to count and many of them are nearly impossible to track down or keep track of.

Some are too small to see, and others are in places too difficult to reach. There are even too many humans spread too far around the globe to ever know with precision exactly how many humans are on Earth at any particular time. That's why scientists tend to rely upon estimates to make educated guesses about populations.

Let's take a look at a few facts and figures that highlight the problem of trying to estimate how many animals there are in the world. First, we don't even know how many types of animals there are in the world, let alone how many individual animals there are.

Scientists have recently estimated that there are approximately 8.7 million species on Earth. They believe that 1-2 million of those species are animals. And what do we know about all those species? Not much! The same study estimates that 86% of all land species and 91% of all sea species have not yet been discovered or described!

Sticking to the species we do know about, let's look at some amazing numbers for particular groups of animals. Scientists believe there are over seven billion humans in the world today. That's a staggering number, but there are more chickens (over 18 billion) than humans. At least we humans do outnumber cattle (1.4 billion) and sheep (1.1 billion).

Those numbers pale in comparison to the insect world, though. For example, scientists estimate there are over 10,000 trillion ants alive at any one time. Based upon those numbers, some scientists estimate the total insect population at 10 quintillion, which is 10 billion billion! That figure has led at least one expert to estimate the total animal population on Earth to be about 20 quintillion, or 20 billion billion!

Did you get it?

Wonder What's Next?

Does gardening always have to be dirty? Find out in tomorrow’s Wonder of the Day!

Try It Out

Are you ready to have some fun with animals? Be sure to check out the following activities with a friend or family member:

How high can you count? Grab a notebook and a pen and get ready to count. Pick a spot in your backyard or a park and make yourself comfortable. Spend at least 30 minutes simply observing the area, writing down every single type of animal you see. Try to keep track of how many of each different type of animal you see. Watch for every type of animal, including insects. Have fun! How many do you count?

Isn't it amazing that the majority of species on Earth haven't been discovered or described? Why do you think this is? Where do you think they're hiding? If you were a scientist interested in discovering new species, where would you look? How would you go about finding new species and describing them? Come up with an action plan for how you might go about exploring the world of undiscovered species. Discuss your plan with a friend or family member.

Despite humans having explored so many corners of our planet, new species are still being discovered and described today. Head over to LiveScience with a family member or friend to explore newfound species! Which one is most interesting to you? Which species is most interesting to your family member or friend and why?

Wonderopolis

Joe

Wonderopolis

Sep 26, 2017

Hi, Joe! We ask that Wonderopolis be listed as the author. Since we do not list the publish date for our Wonders of the Day, you may put the date you accessed this page for information. The following is how you would cite this page:

kaden

Wonderopolis

Apr 27, 2017

Aww that's not very nice, Kaden. Maybe you just haven't found the right Wonder yet. Take a look in our Explore Wonders section and search for something you are interested in learning more about. Good luck!

kadence

Dec 13, 2017

Don't listen to them This site is WONDERful. I learned so much from this site its just that some people are jealous because yaw can actually make a sucessful website. I actually disliked reading but yaw made me LOVE reading. Please ignore mean and rude people and i also hope all of yaw have a WONDERful day 😆

Wonderopolis

Apr 24, 2017

We appreciate you sharing your thoughts about this Wonder. Sometimes the Wonders just get you started WONDERing and researching. We always encourage our Wonder Friends to keep researching online and at the library. Luckily, there are more than 1,800 other Wonders to explore. We hope you check those out. We're sure you can find one you like better! 😃

Wonderopolis

Liv

Apr 21, 2017

Hey wonderopolis! The comment glitch is back. LOL. Sadly, again my comment from yesterdays passage didn't go through! Hopefully it will be there tomorrow! Great passage! (BTW Im not mad about the comment not going through, because its perfectly fine! So don't think I don't like you guys anymore" :)

Wonderopolis

Apr 22, 2017

Thanks for understanding, Liv! When you leave a comment, it is not immediately posted. Our team at Wonderopolis must approve it first. We appreciate you looking our for our Wonder Friends and us, too! 😃

Wonderopolis

Goldenstar

Apr 21, 2017

I liked this wonder. But on the fourth paragraph(Counting the monkey and sloth talking as one paragraph) at the end, between "wide" and the period, the space is highlighted. It's not a big deal, but it annoys me.